Prior to the present invention, o-rings in a standard packed-bore type pressure release valve with a high pressure port and a low pressure port are disposed about a recess created between the flanges of two adjacent spool valve shells. During slow cycling of the valve while under high pressure, o-rings can become dislodged from the recess, causing operational problems. Viton™ material is typically used because it has a greater stiffness in order to prevent the o-rings from dislodging from the high pressure during valve actuation. However, at −40° F., functional testing has revealed that a Viton™ o-ring does not provide a leak-proof seal. To correct the problem, the Viton™ o-ring was replaced with a nitrile o-ring of the same size. Because it is softer than Viton™, the nitrile material provides a leak-proof seal. However, functional testing of the valve with the nitrile o-rings revealed that when the valve is actuated, the resultant high pressure might dislodge the nitrile o-ring, causing interference with the normal operation of the valve.
When the rate of actuation of the valve increases, o-ring dislodgement is minimized. However, depending on the particular application, a high rate of actuation may not always be possible with a valve that relies on a pressure differential method of operation. While the greater stiffness of the Viton™ o-rings eliminates the dislodgement problem, the operational range and performance of the valve is adversely affected as a result.